Simulation Study Of Vacuum-assisted Compression Resin Transfer Molding Process For Stitched Composites

The vacuum assisted compression resin transfer molding(VACRTM)process is an improvement based on the traditional resin transfer molding(RTM)process.Before the resin is injected into the cavity,by increasing the space between the upper and lower molds to expand the injection flow area of the resin,reducing the difficulty of injection and increasing the fiber volume content with vacuum-assisted the process is divided into resin injection stage and mold compression stage,this paper mainly studies the filling process of the resin injection stage.In order to study the resin filling flow law in the VACRTM process,and clarify the influence of the process parameters on the resin filling process,this article takes stitched basalt composite material as the research object.Firstly,the experimental permeability value was obtained through experimental test and compare it with the simulated value to verify the rationality of the model and the simulation process.Secondly,create a meso-cell model and a plate model of the stitched preform,use PAM-RTM software to analyze the flow law of resin inside the material,obtain the relationship between resin filling displacement and filling time,and calculate the permeability under different stitching densities;Analyze the influence of different stitching densities,resin viscosity,injection pressure,and injection scheme on the resin filling process.Finally,the simulation analysis method is applied to specific products to study the VACRTM process resin filling process of stitched composite propeller blades and determine the best process parameters.The results show that:The error between the simulated permeability value and the experimental permeability value is 2.07%,which is within a reasonable error range.Therefore,it is reasonable to obtain the permeability value of the preform through the numerical simulation method;The filling time of the stitched unit cell model is less than the simulation time of the unstitched unit cell model,because the existence of slit holes accelerates the resin filling rate.Due to the existence of the compressed volume space in the VACRTM process,the resin can be quickly filled into the compressed space at the beginning of injection,and then the preform can be infiltrated in the thickness direction,so,it can shorten the infiltration time compared with the RTM molding process the greater the resin viscosity,at the same time,the greater the resin viscosity,the longer the filling time,the greater the injection pressure,the shorter the resin filling time,the resin filling time of boundary line injection and center point injection is much shorter than the resin filling time of boundary point injection;The optimal injection pressure of the stitched composite propeller blades with a length of365 mm and a width of 144 mm is 2×10~5pa,the best solution for glue injection is that the glue injection port is located at the tip of the propeller blade,and the glue outlet is located at the upper and lower ends of the blade root.The filling time is 220 s.